Combine harvesters are provided with a processing system comprising a thresher rotor assembly, as well as a cleaning system. The thresher rotor assembly typically comprises a thresher rotor or cylinder and one or more arcuate, foraminous concaves and separator grate assemblies, through which crop material threshed by the thresher rotor pass to the cleaning system and large residue such as stalks are discharged from the thresher rotor assembly to a chopper. The threshed crop material may comprise kernels of grain, chaff, small pieces of stalk or straw, etc. The cleaning system is used to remove chaff and other residue from, for instance, the threshed grain. Within the cleaning system, an oscillating cascade pan and sieve assemblies of a shaker shoe assembly (hereinafter, also simply shoe), in conjunction with air flow, remove the chaff from the threshed grain. The cleaned grain is conveyed to a discharge auger that elevates the grain to an onboard storage bin, whereas residue such as material-other-than-grain (or MOG) and possibly unthreshed grain is directed over the edge of a bottom sieve assembly of the shoe to a different discharge outlet for recirculation back through the thresher rotor assembly and cleaning system to extract any unthreshed grain. A fan of the cleaning system produces an airstream through the shoe that entrains the lighter, non-grain particles (chaff or generally, lighter MOG) and carries them out, at or towards the rear of the combine harvester.
Different methods have been developed to discharge the MOG to the field. Historically, combine harvesters have used the chopper to chop and spread rotor material and a chaff spreader to spread the shoe material. Recently, combine harvesters of some manufacturers reveal designs where both the shoe and rotor material are provided through a single chopper and distributed as a mix to the field. Although the latter design eliminates the chaff spreader, which reduces complexity, it also tends to choke the cleaning shoe, decreasing shoe performance. Some manufacturers have addressed the choke issue by introducing combine harvesters with ventilation or exhaust holes in the side of the cleaning shoe, which, though alleviating air choke issues, results in the deposit of the lighter MOG directly (e.g., undistributed, such as not distributed transversely at any given point in time) to the ground.